Conventionally, a structure of a vehicle seat is known. In the structure, reclining devices that are capable of adjusting a tilt angle of a seat back are disposed on the vehicle seat. Japanese Laid-Open Patent Publication Number 2002-34697 teaches a structure in which reclining devices connecting a seat back and a seat cushion are disposed on both sides of a vehicle seat. In this structure, a belt retracting port of a seatbelt device is formed in a shoulder portion of the seat back in one side of the vehicle seat.
Further, in the side of the vehicle seat in which the belt retracting port is positioned, the seat back and the seat cushion are connected via the two reclining devices described above that are laterally juxtaposed to each other. Thus, a connection strength between the seat back and the seat cushion can be increased in the side of the vehicle.
However, in the conventional technique described above, the number of the parts and the assembling processes can be increased because the two reclining devices are laterally juxtaposed to each other in one side of the vehicle seat. Therefore, in order to increase the connection strength, for example, a single large reclining device can be used instead of the two reclining devices in one side of the vehicle seat in which the connection strength between the seat back and the seat cushion must be increased. However, as shown in Japanese Laid-Open Patent Publication Number 2003-507101, when each of the reclining devices has an eccentric mechanism in which an external gear wheel revolves along a toothed inner circumferential surface of an internal gear wheel while changing a meshing position therebetween, if one of the reclining devices is simply increased in size, the revolving motion of the external gear wheel of one of the reclining devices can be performed in behavior that is different from the other of the reclining devices.
Thus, there is a need in the art to increase a connection strength of one of the conventional connection devices that relatively rotatably connect a pair of subject components, such as one of the reclining devices described above.